/**
 * StudiedProposition.java
 * 
 * Copyright (C) 2012 - Thibault BUREL
 * 
 * This file is part of MathDraft.
 *
 * MathDraft is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * MathDraft is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with MathDraft.  If not, see <http://www.gnu.org/licenses/>
 *  
 */
package drk.mathdraft;

import drk.mathdraft.proposition.*;
import drk.mathdraft.proposition.builder.*;

import java.util.*;

public class StudiedProposition extends Observable
{
	/*************************************************************************
	 *                          M E M B E R S                                *
	 *************************************************************************/
	private Proposition currentProposition;
	private static volatile StudiedProposition instance = null;
	
	/*************************************************************************
	 *                          M E T H O D S                                *
	 *************************************************************************/
	private StudiedProposition()
	{
		super();
		
		try
		{
			this.currentProposition = NaturalNotation.fromNaturalNotation ("0");
		}
		catch (SyntaxException e)
		{
			// Impossible !
		}

	}
	
	public final static StudiedProposition getInstance()
	{
		if (StudiedProposition.instance == null)
		{
			synchronized(StudiedProposition.class)
			{
				if (StudiedProposition.instance == null)
				{
					StudiedProposition.instance = new StudiedProposition();
				}
			}
		}
		return StudiedProposition.instance;
	}
	
	public Proposition getProposition()
	{
		return this.currentProposition;
	}
	
	public void forceUpdate()
	{
		setChanged();
		notifyObservers();
	}
	
	public void setProposition(Proposition p)
	{
		this.currentProposition = p.copy();
		forceUpdate();
	}
}